In a construction machine such as a hydraulic excavator, since the load factor is high in comparison with such a vehicle as a truck, the possibility that an engine or the like may fail is relatively high. On the other hand, if such a construction machine suffers from a fatal failure, then since expensive repair costs occur and there is such a circumference that there is no choice but to drastically lower the occupancy rate within a repair period, it is demanded to make it possible to handle the maintenance at an initial stage of a failure by performing a failure analysis, a diagnosis of an omen, or the like thereby to prevent a fatal failure of the machine body.
For example, as a technology relating to a failure diagnosis of an engine used for a construction machine, Patent Document 1 discloses a failure diagnosis apparatus for an internal combustion engine in which a cylinder internal pressure sensor is installed in an engine that is a prime mover to detect a failure of a fuel injection valve.
Further, as another technology relating to a failure diagnosis of an engine, Patent Document 2 for example discloses a machine body diagnosis apparatus in which frequency distribution information representative of a relationship between the magnitude and the appearance frequency of a signal relating to engine output power is generated and accumulated and a decrease of engine output power is detected on the basis of the frequency distribution information.